1. Field of the Invention
The present invention relates to a particulate measurement apparatus and system which measure the amount of particulates such as soot contained in a gas under measurement.
2. Description of the Related Art
Conventionally, a particulate measurement system has been known which measures the amount of particulates (e.g., soot) contained in a gas under measurement (for example, exhaust gas discharged from an internal combustion engine or the like) (see, for example, Patent Document 1).
Such a particulate measurement system includes a particulate sensor which is exposed to the gas under measurement and detects particulates. The particulate sensor includes an ion generation section, an electrification chamber, a trapping section, and an auxiliary electrode section.
The particulate measurement system electrifies at least a portion of particulates contained in the gas under measurement in the electrification chamber using ions generated at the ion generation section by means of corona discharge, and measures the amount of particulates based on the amount of ions trapped by the trapping section. Notably, the auxiliary electrode section is maintained at a potential which repulse the ions to thereby assist the trapping of ions at the trapping section.
[Patent Document 1] Japanese Patent Application Laid-Open (kokai) No. 2013-195069
3. Problems to be Solved by the Invention
However, a problem arises in the particulate measurement system described above in that when particulates (soot, etc.) adhere to the particulate sensor, the accuracy in measuring the amount of particulates is lowered or measurement of the amount of particulates can no longer be carried out.
For example, when the insulation resistance between the auxiliary electrode section and the reference potential (ground potential) decreases due to particulates, etc., having adhered to the particulate sensor, an irregular current may flow through the adhered particulates, etc. Also, an irregular current may flow when a voltage application path for applying a voltage to the auxiliary electrode section suffers an electrical anomaly (for example, a short circuit between the voltage application path and the ground). If such an irregular current flows, the amount of ions trapped by the trapping section is in error, which adversely affects the measurement of the amount of particulates.